Screwworm quarantines threaten adoption transport approach to achieving Best Friends’ “90% live release rate” threshold for “no kill” status
AUSTIN, Texas––From agribusiness pundits to zoonotic disease researchers, online commentators were mystified on June 18, 2026 to see Best Friends Animal Society senior director of national programs Brent Toellner lined up to testify to the Texas House Agriculture & Livestock Committee about New World screwworm, a fly-borne disease afflicting mainly cattle.
The Best Friends Animal Society deals mainly with dogs and cats, pushing pit bulls in particular. Toellner especially is a notorious pit bull pusher.
(See Kansas City Pet Project dog attack claims don’t add up.)
“Texas has two things: steers & pit bulls”
Had someone somehow confused pit bulls with steers while setting the Texas House Agriculture & Livestock Committee agenda?
No. Toellner was there, representing the Best Friends Animal Society, because quarantines established to combat the spread of New World screwworm threaten the adoption transport modus operandi that Best Friends has for 20-odd years promoted, ahead of spay/neuter, as the solution to regional dog-and-cat overpopulation.
That means mostly pit bull overpopulation, because other shelter dogs are relatively easily rehomed right where they are..
Move pit bulls from places where shelters are full and few are adopted, the theory goes, to places where they are not yet notorious for unpredictably explosive mayhem, and people can be persuaded to take them home.
Screwworms vs. pit bulls as health threat
Of course adoption transport of pit bulls has not really worked that way. When the Best Friends emphasis on pit bull pushing began, in 2005, pit bulls were about a third of shelter dog admissions. That figure has doubled. Total shelter dog adoptions and killing have both flatlined. Pit bulls are still about two-thirds of all shelter dog euthanasias.
As of 2005, shelter dogs were known to have killed only four people since U.S. shelter dog adoptions began in 1858. Since then, at least 102 shelter dogs, 72 of them pit bulls, have participated in killing at least 61 people.
Neither New World screwworm nor Old World screwworm has ever killed anyone within the U.S., nor are human deaths on record abroad, ugly, painful, and disfiguring as screwworm infections can be.
But human screwworm cases do occur, at about 1% of the rate of detection in cattle.
Neither New World screwworm nor Old World screwworm, similar parasites carried by different fly species, are known to pose any significant direct threat to either dogs or cats.
Why dogs are of screwworm concern
Dogs are of current concern as potential screwworm hosts because a June 3, 2026 USDA Animal & Plant Health Inspection Service report mentioned that New World screwworm had been discovered in a dozen cattle in Texas and New Mexico, plus one dog in New Mexico.
“Questions remain about the infested dog in New Mexico,” observed Isaac Arnsdorf and Lena H. Sun in the June 19, 2026 edition of the Washington Post.
“USDA initially said the dog traveled south of the border. Then officials reversed themselves, Arnsdorf and Sun reported. “The state veterinarian, Samantha Holeck, said there was a language barrier at the clinic that treated the dog, and an interpreter later helped establish that the dog never left home. Officials are still trying to determine how the dog became infested, Holeck said.”
The New Mexico dog appears to be the first canine screwworm victim in the U.S. since November 1, 2007, when the National Veterinary Services Laboratories confirmed a case of Old World screwworm in a Labrador retriever.
Flown to Boston from Singapore, with a one-day layover in Amsterdam, The Netherlands, the Labrador retriever was diagnosed later the same day by a veterinarian in South Weymouth, Massachusetts.
Cats & screwworm
The history of screwworm of either the New World or the Old World variety in cats is even shorter. The totality of relevant veterinary literature in the National Library of Medicine, published in the February 2010 edition of the Journal of Feline Medical Surgery, entitled ‘Myiasis caused by the New World screwworm fly Cochliomyia hominivorax (Diptera: Calliphoridae) in cats from Brazil: report of five cases.”
Researchers Clarissa P. de Souza, Guilherme G. Verocai, and Regina Ramadinha discovered five total screwworm cases, three in strays who “died despite treatment due to the severity of lesions while two were client-owned cats previously treated with cryosurgery,” who completely recovered.
So screwworm can strike either dogs or cats, but evidently not very often.
Explained Jayme Lozano Carver for the Texas Tribune on June 19, 2026, “The parasitic fly lays eggs in open wounds, which then turn into larvae that feast on the living flesh of warm-blooded animals. And it isn’t limited to cattle, livestock and wildlife — anything with a wound is at risk of attracting the fly. This includes cats, dogs and humans.”
Disaster order
Responding to the discovery of screwworm, Texas governor Greg Abbott “issued a statewide disaster proclamation for all of Texas’ 254 counties,” Lozano Carver continued, after which “the Texas Animal Health Commission put quarantine orders in parts of 13 counties.”
“The quarantine orders,” Lozano Carver detailed, “effectively stop all warm-blooded animals, whether they are infected or not, from being moved out of the infested zone to other areas of Texas or other states.
“While this does slow the spread of the screwworm,” Lozano Carver noted, “some animal welfare groups worry it could unintentionally exacerbate animal shelter overcrowding.
Fretted Austin Pets Alive veterinarian Rebecca Giamona, “They will do mass, mass, mass euthanasias if they aren’t allowed to move the animals out of the quarantine zones. There could be thousands of animals dying in shelters because they don’t have the space to continue to cover those animals.”
Mass, mass spay/neuter could prevent that problem.
New York & Pennsylvania not taking Texas animals
Affirmed Emma Burns for KLTV in Tyler, Texas, also on June 19, 2026, “New World screwworm concerns are preventing some rescued East Texas dogs and cats from leaving the state on transport flights.
“East Texas shelters had more than 60 animals lined up for a Wings of Rescue transport to out-of-state partners and adoptive homes,” Burns reported, “but some destination states are no longer accepting animals from Texas as a precaution.
“Kansas Pierce, director of the City of Athens Animal Shelter,” Burns continued, “said New York and Pennsylvania — two of the shelter’s biggest destination states — have paused intake of animals from Texas.”
Precautions & treatment
The Houston SPCA, Lozano Carver mentioned, “is taking precautions to protect the 500 to 600 animals they take in on a weekly basis. For example, Houston SPCA kicked up fly control measures.
But “Many of the Houston SPCA’s precautions are things it did before screwworm,” Lozano Carver continued, citing parasite examinations and treatment routinely done as part of the shelter admission process.
The U.S. Food & Drug Administration, Lozano Carver added, has approved use of Nitenpyram, “an over-the-counter medication in tablet form, to treat screwworm in dogs, puppies, cats and kittens. Three other medications have been approved for farm animals.”
Livestock quarantines
Updated Dan Flynn for Food Safety News on June 21, 2026, “Canada temporarily banned livestock imports from Texas due to confirmed cases of the flesh-eating screwworm, affecting cattle, horses, bison, and other animals who were in Texas within 21 days of crossing the border.
“The U.S. suspended imports of Mexican cattle in May 2026 as the parasite neared the American border,” Flynn continued. “Mexico had supplied about 1.2 million head of cattle annually to the United States, primarily feeder cattle destined for U.S. feedlots.
The USDA Animal & Plant Health Inspection Service, Flynn reported, “has mobilized emergency responses, including sterile-fly releases, import suspensions, and construction of domestic sterile fly production facilities,” and is under pressure from “lame duck” Texas agriculture commissioner Sid Miller to make more extensive use of insecticides targeting screwworm.
Sterile fly shortage
New World screwworm was declared eradicated from the U.S. in 1966, after a federal effort originating in 1933.
However, “Starting in June 2023,” Flynn summarized, “New World screwworm reappeared in Panama, and is spreading across Central America. It’s now been reported in Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Mexico.”
Observed Washington Post reporters Arnsdorf and Sun, “The New World screwworm spread from southern Mexico to Texas in two years when the administration cut staff and funding.
“Agriculture Secretary Brooke Rollins has publicly downplayed the danger and pointed fingers at the previous administration,” Arnsdorf and Sun recounted, “even as experts say the reemergence of a grisly pest confined to South America for decades has exposed shortcomings in the government’s ability to respond.
“Eradicating the outbreak requires targeted releases of sterile flies,” Arnsdorf and Sun said, “but the U.S. won’t have enough sterile flies until a new facility comes online next year at the earliest.”
Budget & staff cuts
Meanwhile, the USDA Animal & Plant Health Inspection Service, “whose responsibilities include screwworm detection and treatment,” Arnsdorf and Sun noted, “lost nearly 2,000 employees last year, more than 20% of its workforce, as the Trump administration downsized the federal government.
“The Trump administration’s dismantling of the U.S. Agency for International Development also cut about $382 million from the United Nations Food & Agriculture Organization, including the Global Health Security Program targeting diseases and pests such as New World screwworm.”
Horse transport
Among the most publicized Trump administration responses to the Texas and New Mexico screwworm outbreaks was halting the export of U.S. horses––about 20,000 a year at present––to Mexico for slaughter.
That move made no sense at all from an epidemiological perspective, since U.S. horses en route to slaughter in Mexico are being trucked south, not north.
Those horses are not going to be transporting screwworm into the U.S.
Apparently the horse traffic south was halted as a retaliatory measure after Mexico on June 9, 2026 blocked the import of about 40,000 U.S. cattle per year, citing screwworm as a pretext, after the Trump administration on May 11, 2025 used screwworm as the pretext for stopping the import of about 1.1 million cattle per year from Mexico.
This has contributed to soaring beef prices in U.S. supermarkets.
(Horse Plus Humane Society photo)
Kill buyers stuck hoarding horses
Logical or not, exulted Horse Plus Humane Society founder Tawny Preisner on Facebook, “Kill buyers who rely on shipping horses across the southern border for quick cash are now stuck hoarding horses on crowded, poorly managed lots that they legally cannot move.”
This in turn, Preisner predicted, means at least a temporary suspension of the horses-for-ransom racket, in which kill buyers extort money from horse rescuers on the pretext that horses will be trucked to Mexico for slaughter otherwise.
However, slaughtering horses where they stand for rendering into pet food remains legal throughout the U.S., if much less lucrative than selling horses for human consumption after slaughter in either Mexico or Canada.
Florida outbreaks
The most recent previous screwworm detections of note in the U.S. have come in Florida.
The USDA on June 8, 2000 honored Florida equine veterinarian Paul Wollenman, 50, for recognizing screwworm larvae on a six-year-old polo pony named Gitano, who had just arrived from Argentina and had cleared a three-day quarantine. Gitano was safely treated.
A screwworm outbreak that killed 135 endangered Florida Keys miniature deer in 2016-2017 was quelled by the February 2017 release of more than 101 million sterile screwworm flies.
The USDA declared the outbreak over with on April 12, 2017, but that was scarcely the end of the issue.
Cats in Cuba
In August 2017 the U.S. Navy reportedly used screwworm quarantine rules to shut down a cat rescue project called Operation Git-Meow at the Guantanamo Navy Base in southeastern Cuba, founded by resident Erika Kelly.
“An official working at the base best known for its War on Terror prison said the group had become a bit of a pest,” explained Carol Rosenberg for the Miami Herald, “planning to open a shelter, engaging too much with the U.S. Army veterinarian whose primary job is to care for base families’ sick pets, and being a general drain on Department of Defense resources.
“Primarily at risk,” Rosenberg explained, “is the new program of evacuating cats to homes in the United States because the new restrictions may make it difficult to get a certificate from the veterinarian proving the cats have been vaccinated and checked for screwworms.”
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Such a shame so many large organizations don’t prioritize spay/neuter. So much more suffering, then combine that with the crazy “no kill” policies (which I call slow-kill) and we have more dogs and cats out there then ever before.
Dallas is in such bad shape with overpopulation of dogs and cats, every shelter, rescue and foster home aren’t taking any in –– it makes me lose hope.
Excellent reporting
In agreement with both previous posters, and thanking you for this coverage.